Soil pH measures the acidity or alkalinity of the soil on a scale from 0 to 14. A value of 7 is neutral, while numbers below 7 indicate acidity and numbers above 7 indicate alkalinity. Soil pH controls nutrient availability, determining how easily plants absorb necessary elements like iron, manganese, and phosphorus. If the pH is outside a plant’s preferred range, nutrients can become chemically locked up and unavailable to the roots. Florida’s soil pH varies widely depending on the specific location and underlying geology, meaning there is no simple answer to whether the soil is acidic.
The General Nature of Florida Soil pH
Florida’s soils present a diverse spectrum of pH levels, defying a single classification. The median soil pH across the state is around 6.1, which is slightly acidic. However, the overall range stretches from highly acidic to extremely alkaline, approximately 4.5 to 8.5. Soils in Central and North Florida, particularly those under pine flatwoods, tend to be naturally acidic. Conversely, soils in coastal areas and throughout South Florida are typically neutral to alkaline.
Geological and Environmental Influences
The variation in Florida’s soil pH results directly from the state’s unique geological structure and climate. The entire Florida peninsula sits atop a foundation of limestone bedrock, composed primarily of calcium carbonate. In South Florida and coastal regions, this limestone is often shallow, imparting alkalinity to the topsoil and resulting in high pH levels, typically between 7.8 and 8.4.
In contrast, the sandy soils prevalent in Central and North Florida have a low capacity to resist pH changes. High rainfall in these areas causes rapid leaching of positively charged elements like calcium and magnesium, which neutralize acidity. This washing away of basic elements leaves behind hydrogen ions, increasing the soil’s acidity over time. The long-term use of certain fertilizers, such as those containing ammonium, can also contribute to this acidification process.
Practical Impact on Plant Selection
The specific pH of the soil dictates which nutrients are accessible, fundamentally influencing plant selection. In the alkaline soils of South Florida, high pH causes “nutrient lockout,” making micronutrients like iron (Fe) and manganese (Mn) insoluble. This deficiency manifests as interveinal chlorosis, a yellowing between the leaf veins, even though the nutrients are present.
Acid-loving plants, such as blueberries, azaleas, and gardenias, struggle when the pH rises above 5.5 because they cannot absorb sufficient iron and manganese. Conversely, many native Florida plants and tropical fruits, like mangos and avocados, are adapted to tolerate the state’s high-pH, calcium-rich soils.
Testing and Adjusting Soil pH
Determining the specific pH of your soil is the first and most practical step for any gardener or homeowner. While home kits offer a rough estimate, a professional soil test from a local extension office provides an accurate pH reading and specific recommendations for amendment. These professional tests also measure the soil’s buffering capacity, indicating its resistance to pH change, which is relevant in Florida’s sandy soils.
For acidic soils, the pH is raised by applying a liming material like calcium carbonate or dolomitic lime. Dolomitic lime is often recommended because it also supplies magnesium, a nutrient frequently deficient in sandy environments. To lower the pH of alkaline soils, elemental sulfur is commonly added, which slowly oxidizes to form sulfuric acid. However, in highly alkaline soils with underlying limestone, this adjustment is often temporary, making the selection of pH-tolerant plants a more sustainable strategy.